1. Field of the Invention
This invention relates to data processing and more particularly to storing signals representative of an image.
2. Description of the Prior Art
Recently there has been a plethora of scientific activity directed to processing an input image to provide, for example, a processed image which is comprised of desired features of the input image. A signal representation of the input image may be stored in a digital computer which provides a signal representation of the processed image. The input image is usually provided on an image bearing medium, such as a film.
When a television camera scans an image, an array of closely spaced parellel lines, known as a raster, may be regarded as being successively traced on the film by a line of sight therefrom to the camera. The camera provides a video signal having an amplitude representative of an element of the input image on the film at an intersection thereof with the line of sight. The video signal is provided to an analog to digital converter which is connected to the computer.
In response to the video signal, the converter provides a group of digital signals collectively representative of the amplitude of the video signal. Accordingly, the video signal is converted to digital signals whereby a signal representation of the element is provided to the computer for storage therein.
A digital signal may have one of two values, referred to as ONE and ZERO, respectively. ONE is typically represented by approximately five volts whereas ZERO is typically represented by approximately zero volts. It should be appreciated that the digital computer can only store digital signals (not video signals).
It should be understood that the video signal is one of a multiplicity of video signals provided by the camera during the tracing of the raster. The multiplicity of video signals are respectively representative of substantially all elements comprising the input image. Each one of the multiplicity of video signals is converted to a group of digital signals by the converter whereby the computer stores groups of digital signals representative of the input image.
Typically, the multiplicity of video signals is provided to a television monitor display. In response to the multiplicity of video signals the monitor display provides a visual representation of the input image.
In commercial television, it is a standard practice to trace in one sixtieth of a second a raster comprised of raster lines which are each traced in 53 microseconds. It is usually desirable to provide a display representative of at least 450 elements along a raster line. To successively provide groups of digital signals respectively representative of the 450 elements along a standard raster line, the converter operates rapidly. The rapid operation causes the converter to be complex, expensive and unreliable.
When the raster is traced at a rate slower than one sixtieth of a second, the converter operates at a correspondingly slower rate. However, the visual representation (on the monitor display) may appear to flicker.